This application claims the priority of Japanese Patent Applications Nos. 2000-196394 and 2000-196395 filed on Jun. 29, 2000 which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electronic endoscope device and particularly relates to a circuit configuration of measuring a light receiving state of an image pickup device in a separation photometric area set on an image pickup surface for controlling brightness of an image.
2. Description of the Prior Art
The electronic endoscope device displays an image of an observed object on a monitor by applying signal-processing with a processor device or the like to a picked-up image signal obtained by a solid image pickup device [CCD (Charge Coupled Device) provided in an electronic endoscope. Then, in this electronic endoscope device, the light receiving state in the above described CCD is measured, and the control for making the brightness of the image of the observed object displayed on the above described monitor fine is performed.
In FIG. 7(A), a conventional separated photometric area set on the image pickup surface of the CCD is shown. As shown in the figure, this square photometric area EA has one to seven separated areas on the image pickup surface, and to this photometric area EA, the actual image pickup area (circular oblique hatching part) that is the luminous flux range of the image formation face of the objective optical system is FA. In this photometric area EA, the light receiving amount (luminance) of each of the separated areas 1 to 7 is detected, and for example, the central area 4 has a weighting factor of 2, the left and right areas 3 and 5 thereof have a weighting factor of 1.5, and the upper and lower areas 1, 2, 6, and 7 have a weighting factor of 1, and by multiplying each light receiving amount by the above described weighting factor, the total light receiving state (brightness) of the photometric area EA is determined.
Then, on the basis of this light receiving data of the photometric area EA, in the electronic endoscope device, the iris control is performed in the light source device, or the electronic shutter control is performed in the above described CCD. That is, in the iris control circuit of the light source device, the diaphragm opening amount is controlled on the basis of the above described light receiving data, and by the output control of the light radiated to the observed object, an image with constant brightness can be obtained. Furthermore, in the electronic endoscope that performs the electronic shutter control, the charge storage time of the CCD is controlled on the basis of the above described receiving light data, and by controlling the incidence amount of the light of the image of the observed object (exposure value), an image with fine brightness can be obtained.
Object of the Invention
However, the brightness control based on the above described conventional separated photometric area has had such a problem that the meaning and effect of performing the photometry for each separated area is diluted in the case where electronic endoscopes in which the size of the image pickup area is different are connected to the processor device or the like. That is, depending on the kind of the electronic endoscope, the actual image pickup area (image formation face luminous flux range) set by the objective optical system at the tip thereof is different, and as shown in FIG. 7(B), for example, there is a case where an image pickup area with a small FC is set (narrow angle scope), and even in the case where such an endoscope is connected, the photometric area set on the processor device side is EA. As a result of this, as understood from FIG. 7(B), in the total photometry, the contribution of the light receiving amount of the central area 4 becomes larger than those of the peripheral areas 1 to 3, 5 to 7, and in the case where a projection or a depression exists at the central part, the peripheral part may become dark or the peripheral part may become too bright.
Furthermore, as shown in FIG. 7B, there is such a problem that when the actual image pickup area FC becomes smaller than the case of FA in FIG. 7A, the operational range of the diaphragm member thereof is narrowed in the iris control of the light source device or the like. That is, as shown in FIG. 8, in the iris control, it is preferable that the operational position of middle brightness is set at the central position HA of the diaphragm member movable range, and that the diaphragm member can be moved in the closing direction and opening direction from this position HA, but when the total light receiving amount in the photometry is decreased, the above described operational position of middle brightness shifts to HB. As a result of this, as shown in the figure, the operational range g in the direction of opening the diaphragm member is narrowed, so that fine light volume control cannot be performed.
Furthermore, in the electronic endoscope device, the light guided by a light guide is radiated to the observed object, and the reflected light thereof is incident on the image pickup surface of the image pickup device through the objective optical system, but the light distribution characteristic (light intensity distribution) caught by this image pickup surface (or the image pickup area) is different in the size of the above described actually set image pickup area, and there is such a problem that the light receiving amount measured in each of the separated areas 1 to 7 becomes unequal because of this difference in the light distribution characteristic.
FIGS. 9(A), 9(B) show the light distribution characteristics in the horizontal direction in the image pickup areas of FIGS. 7(A), 7(B), and FIG. 9(A) shows the light distribution characteristic of the image pickup area FA in FIG. 7(A) (standard scope), and FIG. 9(B) shows the light distribution characteristic of the image pickup area FC in FIG. 7(B) (narrow angle scope). S in FIGS. 9(A), 9(B) is a horizontal synchronous signal, and this light distribution characteristic shows the light intensity distribution along the horizontal scanning line. In the case of the standard scope, as shown in FIG. 9(A), a comparatively smooth light intensity distribution is made, but in the case of the narrow angle scope, as shown in FIG. 9(B), the light distribution characteristic is made such that the light intensity at the central part is high and it suddenly rises. Such a light distribution characteristic is similar in the directions of all orientations of the image pickup area FA, and because of this difference in the light distribution characteristics, a difference is caused in the light receiving amounts of the central part 4 and the peripheral areas 1 to 3, 5 to 7.
The present invention is made in view of the above described problems, and it is an object thereof to provide an electronic endoscope device, wherein it is possible to perform the brightness control satisfactorily by equalizing the photometric conditions of the separated photometric areas, and furthermore, the operational range in the iris control or the like is also not narrowed, even in the case where the actual image pickup area or the light distribution characteristic thereof changes.
In order to attain the above described objects, the present invention comprises: various kinds of electronic endoscopes to which an objective optical system and an image pickup device are provided; a main unit which is arranged so that these electronic endoscopes can freely be connected, and which controls brightness of an image based on the light receiving state of the above described image pickup device; a photometric circuit which is provided to this main unit, and which measures the light receiving state of the above described image pickup device by the photometric area having a plurality of separated areas set in the image pickup surface of the above described image pickup device; and a determination circuit which gives a different weighting to the measured value of the separated area in the above described photometric area according to the light distribution characteristic of the image pickup area of the above described image pickup device, and which determines the brightness of an image.
The weighting in the above described determination circuit can be given considering the area ratio of each separated area of the above described photometric area.
It is possible that the image pickup area information including the above described light distribution characteristic is given to the above described electronic endoscope side, and that this image pickup area information is read on the above described main unit side, and that the above described weighting corresponding to this is set.
According to the above described configuration of the present invention, for example, a processor device on the main unit reads the image pickup area information (including size and light distribution characteristics) from the electronic endoscope side, and gives weighting to each separated area of the photometric area according to the light distribution characteristic of the actual image pickup area set on the image pickup surface of the image pickup device. It is preferable to set this weighting not only by considering the light distribution characteristic but also by considering the change of the area ratio of the image pickup area whose size is changed to the photometric area (change for each separated area). Consequently, even if electronic endoscopes different in light distribution characteristics or sizes of the image pickup area are connected to the processor device, non-uniformity of the photometric condition of the central area and the peripheral areas in the photometric area is canceled, and an image with a fine brightness can be formed.
Furthermore, another invention comprises: the above described various kinds of electronic endoscopes; the above described main body; a photometric circuit which is provided on the main body side, and in which various kinds of photometric areas having a plurality of separated areas and a different total size (area) are arranged to be able to be set in an image pickup surface of the above described image pickup device, and which measures the light receiving state of the above described image pickup device by the above described selected and set photometric area; and a control circuit which selects a photometric area in the above described photometric circuit according to the size of an image pickup area of the above described image pickup device determined by the objective optical system of the above described electronic endoscope.
In this case, the information of the above described image pickup area is also given to the above described electronic endoscope side, and on the above described main body side, this image pickup area information is read, and a photometric area corresponding to this is set.
According to this other invention, the ununiformity in the photometric conditions is furthermore canceled, and in the meantime, it does not occur for the operational range of the diaphragm member to be narrowed in the light source iris control or the like.